Constants for freezing-point depression and boiling-point elevation calculations

Question

Constants for freezing-point depression and boiling-point elevation calculations at 1 atm: *When using positive K_f values, assume that Delta T_f is the absolute value of the change in temperature. If you would prefer to define Delta T_f as "final minus initial" temperature, then Delta T_f will be negative and so you must use negative K_f values. Either way, the freezing point of the solution should be lower than that of the pure solvent. If a 0.690 m aqueous solution freezes at -2.20 degree C, what is the van't Hoff factor, i, of the solute? K_i values can be found here. i = Number

Explanation / Answer

Given that,

molality of the solution, m = 0.690 m

Kf of water = 1.860C/m

Depression in freezing point = 0.00 - ( - 2.20 ) = 2.20 0C

van't Hoff's factor, Kf = ?

We know the formula,

Depression in freezing point = i * Kf * m

2.20 = i * 1.86 * 0.690

i = 1.71

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